Episode 12: Turning old cell phones into forest guardians

National Geographic Explorer Topher White has found that listening for the sounds of chain saws through hundreds of recycled cell phones might give us a chance to fight illegal logging.

In Sirukam, on the Indonesian island of Sumatra, Topher White installs a sensor built to stream audio to the cloud. It’s a tool that could detect the telltale growl of chain saws in protected tracts of forest, potentially helping rangers and other officials to stem illegal logging.
Photo by Thomson Reuters Foundation/Harry Jacques

When a tree falls in the forest and no one is listening, it does make a sound. The sounds of truck engines and chain saws, that is. As illegal timber harvests thin out the world’s forests, National Geographic Explorer Topher White is working with environmental stewards to stop the logging before it happens—by listening for the sounds of loggers through hundreds of recycled cell phones nailed high in treetops from Indonesia to Eastern Europe.

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(Rainforest sound)

PETER GWIN (HOST): On a hot day in 2013 in a forest in Sumatra, surrounded by tall trees and the deafening sounds of jungle life, National Geographic Explorer Topher White began placing the first versions of a device he designed to detect illegal logging.

TOPHER WHITE (CEO, RAINFOREST CONNECTION): We were putting them along the outskirts where they expected there'd be logging.

GWIN: He’d gotten a tip that this small patch of forest had been a target for black market lumberjacks and local rangers were having a hard time catching them. They were eager to test out Topher’s devices to see if they could help. That day, Topher was scrambling to get the technology ready for their first test run.

WHITE: Anyone who knows me, you know, that I, like, barely managed to get any semblance of the hardware finished like the night before leaving.

GWIN: The devices record sounds of the forest and analyze them for the dead-giveaway vibrations of a chainsaw.

WHITE: You know, I think we're putting up like the second or third device ever, and I get this alert on my phone that this thing heard chainsaws, you know, and I’m like, Whoa, everyone quiet down.

GWIN: The forest is loud! Between the cicadas and the songbirds and other noises, a human might not pick up on the distant buzz of a gas engine.

WHITE: And it's true that in the distance, you can barely hear the chainsaw, but no one had really picked it up. And this set off this amazing reaction of everyone—like two guys jump on the motorcycles, the rest of us set off across the forest. And they go and they confront the loggers.

GWIN: Illegal logging is a multimillion dollar industry which is destroying forests all over the world, accelerating climate change, and shrinking the habitats of endangered species. But policing it isn’t easy. A handful of rangers might have to watch over thousands of acres of trees. But Topher White hopes his guardians can make a difference.

WHITE: And I'm just like, what? This is amazing. This is exactly what I'm hoping for.

GWIN: I’m Peter Gwin, editor at large at National Geographic magazine, and you’re listening to Overheard, a show where we eavesdrop on the wild conversations we have here at Nat Geo and follow them to the edges of our big, weird, beautiful world.

If a tree falls in a forest and no one is around to hear it, guess what? It does make a sound. And that sound just might be recorded by Topher White. What else is that technology capable of? It just might be that listening to the forest is the new frontier of conservation and exploration.

More after the break.

(Sound of gibbons)

WHITE: Gibbons are these amazing apes. They live in Southeast Asia. They sing amazingly fluidly and loudly to each other, from great distances in the forest. I knew none of that stuff when I was a child. All I knew is that they were the loudest animals at the zoo, and so they were the first thing we wanted to see when we would get in there. And that’s when you discover all these other amazing things about them.

GWIN: Topher’s early career actually had nothing to do with conservation. In 2011 he was working in France, managing the website for a nuclear fusion lab. But his childhood fascination with gibbons stuck with him, and he found an opportunity to see them in the wild.

WHITE: When things were going OK, I figured I'd take a vacation out there and volunteer at this gibbon sanctuary.

GWIN: The sanctuary was in the South Pacific island of Borneo, home to two endangered species of gibbons. They’re disappearing because of deforestation; half of the island’s natural vegetation has been destroyed over the last 40 years.

WHITE: This is the first time that I ended up in the rainforest anywhere. When you wake up in the morning, it feels like you're on another planet. And that's partially because the forest itself is noisy. So imagine, you know, that you have these like whoops and cries and swings that are nonstop. And you begin to realize the fact that they are speaking to each other, in a certain way.

GWIN: The gibbon sanctuary’s mission is to raise rescued apes in captivity and manage reserves for wild gibbons.

WHITE: We often think that our ability to move from one place to the next is the same as an animal. But you know, if there aren't these super tall trees, the monkeys don't have a way to move through the forest. They're afraid to move through gaps. A single road being cut through a forest that may be only three meters wide is an impenetrable chasm that keeps animals stuck on one side or the other.

GWIN: Keeping the forest connected was vital to the work of the gibbon sanctuary. The reserve was off-limits to resource extraction and was guarded by a handful of rangers. So it was a shock to their guide when they stumbled across a logging site nearby.

WHITE: It was really interesting to me in that moment to see the head of this organization, who was giving us the tour—just how frustrated and broken he felt at that moment. And just a few hundred meters away, five minutes, 10 minutes’ walk from the ranger station, somebody could be logging in their reserve—and get away with it—in a relatively small space.

GWIN: In 2015 the Indonesian government reported that 30 percent of their timber industry comes from illegal sources. And that logging often lays the groundwork for sweeping deforestation.

WHITE: So illegal logging is the gateway activity to the wholesale destruction of the forest.

GWIN: Topher says there’s a lot of demand for hardwood like teak and mahogany, which feed a thriving black market. And once these loggers build a road into the forest, that road can be used to harvest other trees and clear land for farms.

WHITE: And so over the course of just a few years after this road that was created by illegal logging, you'll see the forest completely disappear.

GWIN: Wow. Wow. And where does this lumber end up?

WHITE: The lumber ends up all over the place. So to Asia, Japan, China, the United States, Europe. I think if you find yourself using exotic hardwoods, it's definitely a red flag.

GWIN: The U.S. bans imports of illegal lumber, but it can still make it to the shelves of local retailers when the true source of the wood is hidden in the shell game of the global supply chain. For example, in 2016 the U.S. government fined Lumber Liquidators 13 million dollars for importing flooring made from illegal wood. In that case, the trees were harvested from protected forests in Russia, and then the logs were shipped to China–which has fewer regulations on wood–and then cut into planks for hardwood floors, to be sold to U.S. consumers.

WHITE: At the consumer level. It's extremely difficult to do, if not impossible. These black market networks exist by virtue of things getting lost or added to, like an entire industry based around that.

GWIN: While he was at the gibbon sanctuary, Topher felt like there had to be a way to detect illegal logging without patrolling the entire forest on foot. So he started brainstorming ideas and running them by the head of the organization.

WHITE: And so I came up with a list of like four or five ideas. And at dinner that night, I just kind of like talked to him about it and he's like, “Yeah, that's the one. That's the one that I think will work.” The idea was that we could listen to the sound of the forest, have something up in the trees that would capture the sounds, and pick out the sounds of chainsaws and then alert them.

GWIN: Like a lot of the developing world, this part of Indonesia had cell phone service long before other types of infrastructure.

WHITE: They had no running water, they had no roads, they had no electricity. But they had cell phone service. So he's like, Please build that one—we’ll be able to get the alerts on our phones.

GWIN: So Topher, can you kind of like just walk me through how the thing works.

WHITE: So the way this is, the way this whole system works is that you have this device up in the treetops. It's solar powered. It listens to all the sounds of the forest, every second, every minute, every hour, every day. It captures all of this, compresses it, and sends it up to the cloud, And so once it gets to the cloud, we are able to analyze it for any number of things. Chainsaws, gunshots, you know, trucks, voices, all in real time. And then if there's a threat there, we're able to send an alert back to people on the ground through some apps that we build that then allow them to get an alert, listen in, and respond.

GWIN: What's the device in the trees? How did you build that?

WHITE: So these devices in the trees, we call them guardians. As I was going through all this, I realized that you could go on eBay and buy an old Android smartphone for like less than five dollars in 2012. And suddenly realized that cell phones can do literally everything they're supposed to do in that process, except for power themselves. So for the longest time, the “guardian” was just a very, very souped-up phone case, allowing it to remain solar-powered and to have a more powerful microphone.

GWIN: So you basically have a used cell phone and this solar panel that you've designed and some software that you've added that can listen for certain sounds. That's essentially what this thing is, right?

WHITE: Yeah. I mean, I had no idea how to build a chainsaw-detection algorithm whatsoever.

GWIN: Topher was a little stuck. He didn’t know if detecting chainsaws was even possible, and didn’t know anyone he could ask for help. So he pulled the technologist’s equivalent of a Hail Mary. He knew that Cornell had a famous lab for wildlife recordings. He scraped together money for a plane ticket and a rental car, and he just showed up.

WHITE: And I drove out to Cornell Lab of Ornithology. I flew out there and got a rental car, went up, slept in the car in front of the building. Waited till I saw someone go in, and went up and asked if they and told him about this project and asked if they could help me. And a really great guy named Yu Shiu sat with me for the afternoon and showed me how to detect chainsaws. It was the most amazing thing.

GWIN: OK. To me the amazing part is that he slept overnight in the parking lot instead of sending the guys an email. But, hey, one way or another, Topher finally had everything he needed: The modified cell phones that could send audio to the cloud, solar power to keep the things running, and an algorithm to detect chainsaws.

He was finally ready for a field test. So he went back to Indonesia. And that’s where—as he and the rangers were setting up his first guardians—they got the alert that one of the devices had heard a chainsaw.

WHITE: And I had no idea what was going to happen. I didn't realize whether—I don't know if Indonesia is dangerous or not in these situations.

GWIN: Were you nervous?

WHITE: I was pretty nervous. You know, this kind of got super intense, super quickly in that particular moment.

GWIN: Yeah.

WHITE: But you know, I got to get, major, you know, credit to the rangers who knew exactly what to do. And they go and they confront the loggers and they're like, “Look, you're over the line very slightly. Don't do this again. If you do, we can stop you.” And from this point forward, we'll know when you go over the line. And so much, so much confidence was built around that particular moment.

GWIN: Topher used that first success to start a crowdfunding campaign and expand his proof of concept into something bigger: a start-up called Rainforest Connection. The idea gained a lot of publicity, which then spread the idea to other conservation groups.

WHITE: Lots of requests came in. All over Africa. You have them from all over Latin America. Yeah, from Southeast Asia. You know, there was an assumption that we would, you know, expand in Indonesia.

GWIN: Right. Were you surprised by how many people were reaching out to you, like does this give you a sense of the scale of the problem you were tackling?

WHITE: So it was surprising to see that people were picking up on it. But we were kind of in it, you know, we believed in the technology. I believed in it. It wasn't—it felt right. It felt true. What I didn't appreciate was the distance that still had to travel between where we were and actually being useful to those groups.

GWIN: Topher says he got really lucky with those first guardians. In that pilot project, they were able to stop their first loggers almost immediately. But as his project grew, so did the complications.

WHITE: What we found when we started getting into other areas was how complicated that whole process actually becomes. And even to this day, you still have to solve new problems in most places that you go to, based on new things you discover that you couldn't have predicted if you tried.

GWIN: Well, give me an example of that. So like you come to Cameroon as your next place. What did you have to do differently in Cameroon?

WHITE: Well, so in Cameroon is where you came into—a lot of things change. The biggest issue is there's no light at the bottom of the tree canopy. There's no cell phone service at the bottom of the tree canopy. So that was the point at which we realized that we couldn't make this technology useful unless we climbed to the tops of trees, which I didn't know how to do at the time. And so I learned how to do it.

GWIN: Wait a minute, back up a second, Topher. You need your devices higher in the trees. How do you do that? What is the key to climbing super tall trees?

WHITE: Yeah, essentially the way it works is you will take this big slingshot. You’ll take a weight and you’ll take a string. And you have to shoot this weight up over that branch into the tree canopy in the right place. And it comes back down. And then you use that string to pull up a heavy rope that you will then climb on. And of course, when you get up in the tree, there's a lot more going on than there was on the ground sometimes.

GWIN: Like what? You mean like animal activity?

WHITE: Insects are 100 percent in control. They—if they want to come lick you, they will. If they want to come bite you, sting you, they'll do that. And they'll usually do it, not one at a time, but like a thousand at a time. And so that's just kind of the way it is. So you get to the top of a tree, the first thing that happens is the bees start showing up. There's like not really any salt out there. There's no salt at all. So I'm like this big, amazing salt lick. You know, that's all that I am. And the bees start showing up to come lick you. They don't want to sting you. They just want to come lick you. You know, and at the same time, you are suddenly showing up in the middle of these sort of treetop gardens, which are the territory for squirrels, by extension, snakes. But even more so, termites and ants. And the moment you show up there, they will attack you.

GWIN: Facing salt-hungry bees and startled squirrels was the easy part of the job. The hard part happened down on the ground. When a chainsaw buzzes somewhere in a protected forest, how do you stop it?

WHITE: I assumed initially that you'd have these groups of rangers like tribesmen, NGOs, and that they would catch loggers. I didn't think too much further than that. What are they supposed to do then, right?

GWIN: For many of the rangers the idea of stopping a crime in progress is very daunting.

WHITE: If you think that you're going to have to go stop a logger, take a truck, seize their equipment, and then figure out what to do with the loggers. You know, what—you gonna drag them to the police station that's 100 kilometers away? Like that’s way too much of a commitment that becomes too scary to take on.

GWIN: Topher said that since making arrests in these remote areas can be so difficult, his team started trying to head-off would-be loggers before they did any real damage.

WHITE: For us, once a crime has been committed, once trees have been cut, once these things are then loaded up on a truck, that's when actually the stakes go up big-time. Not only is there money involved for it to be sold, but also a crime has been committed, so people are worried about the consequences of it. That's why they want to react as quickly as possible when that stuff comes in. Because the sooner you get there, the lower the stakes and the less likely it is that people will get hurt. But it's ultimately up to the rangers how they react.

GWIN: Each forest is controlled by different laws and cultures, so it’s not enough just to provide the trees with an alarm system.

Actually preventing logging means that Rainforest Connection has to build relationships with people on the ground.

WHITE: The idea that there's a criminal justice system to take less pressure off of is optimistic in and of itself.

GWIN: Often, protection of the trees is up to local groups like the Tembé, an indigenous group in northern Brazil.


GWIN: Pedro Rosa is Rainforest Connection’s representative in Brazil.

ROSA: The forest alive is life for them. So this is like survival. They need this to be alive, to be themselves and be who they are.

GWIN: The Tembé live on land set aside for them by the Brazilian government, yet keeping loggers and ranchers out is largely left up to them. Pedro has been helping the Tembé set up guardians throughout their reserve.

ROSA: The Tembé said, after you put your guardians over there, we've done like three or four patrols. So the loggers said, OK, we're not going this space anymore because the Tembé are coming in.

GWIN: He says the guardians make the Tembé’s patrols more effective, but there’s still a lot of work to be done.

ROSA: What happens? Deforestation border just changes, right? So they move on from one place to another place. It's kind of endless.

GWIN: Because of the emphasis on deterrence and the complications of local law enforcement, impact is difficult to measure. At the minimum, the guardians are an effective tool for pinpointing illegal activity like logging and poaching. 

But detecting chainsaws isn’t the only thing they are good for. Rainforest Connection has another mission: preserving the sounds of these rich ecological landscapes.

WHITE: The complexity of what's happening in the rainforest—any forest, any soundscape—is intense. You have all these animals vocalizing and over the course of their evolution and of course of their behavior, they've come to occupy their own space. But the ways in which they interact with each other, not just among the species but across species, is very subtle. You can't see more than 20 feet in front of you, but you can hear a kilometer away. And that's how they've evolved to exist and to interact. And there's so much subtlety in there that we can only pull out with this technology.

GWIN: Using artificial intelligence, Rainforest Connection has been able to identify 629 different species so far. It’s proving a valuable tool for monitoring the health of ecosystems and studying animal behavior. And as technology improves, so will the possibilities, like detecting animals that are trying not to be heard.

WHITE: Imagine this scenario: a jaguar is walking through the forest. These are essentially hunters. You know, they're not making noise. We're never going to hear those things. They may not be vocalizing, but most of the time, the rest of the animals are talking about them, you know? And so don't listen for jaguars—listen for the things that happen when jaguars there that other animals are saying—they're putting out warning calls. Maybe they're quieting down. And that's where I think we're going, very, very shortly.

GWIN: The more audio they have to work with, the easier it will be to discover patterns like this. So Topher and Rainforest Connection are trying to record all the audio they can get.

WHITE: Our moonshot for the next ten years would be to gather one million years of continuous audio—one million years of audio from all over the world.

GWIN: And considering the health of these ecosystems, this project has extra urgency.

WHITE: Climate change has begun; we're in it. It's happening. We are kind of the war photographers, so to speak, of climate change when it comes to gathering acoustics.

GWIN: Topher sees this as maybe our only chance to record this moment. And he has a point. There’s a long list of species that have already gone extinct, remembered only through the technology that was available at the time. We only have illustrations and bones of the dodo bird. We only have a few minutes of black-and-white film of the Tasmanian tiger.

(Sound of gibbons)

WHITE: And so that's a responsibility that I think we have. What are the secrets that can be unlocked in the truths that we can capture now, that even we aren't curious to know about that others will be in the future?

GWIN: If Topher White has his way, future generations will be able to hear the fulsome songs of gibbons echoing through healthy forests in Borneo and not just in speakers and headphones.

If you like what you hear and want to support more content like this, please rate and review us in your podcast app and consider a National Geographic subscription. That’s the best way to support Overheard. Go to natgeo.com/explore to subscribe.

Deforestation is a huge problem that needs institutional change as well as innovative ideas like Topher’s. One group of researchers is using waste from coffee production to help destroyed forests recover.

We’ve included a link to the story in our show notes along with other interesting links like the last known footage of a Tasmanian tiger, and Rainforest Connection’s website, where you can listen in on real-time wildlife recordings from all over the world.

All this and more can be found in our show notes, they’re right there in your podcast app.


This week’s Overheard episode is produced by Brian Gutierrez.

Our producers are Khari Douglas, Ilana Strauss, and Marcy Thompson.

Our senior producer is Jacob Pinter.

Our senior editor is Eli Chen.

Our manager of audio is Carla Wills.

Our executive producer of audio is Davar Ardalan.

Our fact-checkers are Robin Palmer and Julie Beer.

Our photo editor is Julie Hau.

Hansdale Hsu sound-designed this episode and composed our theme music.

This podcast is a production of National Geographic Partners.

The National Geographic Society, committed to illuminating and protecting the wonder of our world, funds the work of National Geographic Explorer Topher White.

Whitney Johnson is the director of visuals and immersive experiences.

David Brindley is National Geographic’s interim editor in chief.

And I’m your host, Peter Gwin. Thanks for listening, and see y’all next time.


What happens when a tree falls in a forest and no one is listening? The sound starts with truck engines and chainsaws and ends with a small piece of forest being silenced. Illegal logging is slowly thinning out the world’s forests, paving the way for widespread deforestation. With limited resources and difficult terrain, it’s a hard problem to tackle. National Geographic Explorer Topher White—who considers himself a war photographer for climate change—has found that by listening for the sounds of logging through hundreds of recycled cell phones nailed high in treetops from Indonesia to Eastern Europe, the stewards of the world's trees might have a chance to detect and prevent illegal logging.

For more information on this episode, visit nationalgeographic.com/overheard.

Want More:

Check out this article to learn more about how illegal lumber makes its way into the global supply chain.

National Geographic has detailed explanations of both gibbons and deforestation.

Take a look at this project to use waste from coffee production to help renew destroyed forests.

Also Explore:

Take a look at the last known footage of a Tasmanian Tiger.

To learn more about Topher White and the Rainforest Connection, take a look at their website.